Motion compensation is used in video compression to achieve compression efficiency. A current picture is predicted from a reference picture, and only the difference between the current picture and the prediction is encoded. The higher the correlation between the prediction picture and the current picture, the higher the compression efficiency. However, in some video sequences, particularly fading sequences, the current picture is more strongly correlated to the reference picture scaled by a weighting factor than to the reference picture itself.
Weighted prediction (WP) is a useful tool when the current picture is more strongly correlated to the reference picture scaled by a weighting factor than to the reference picture itself. Modern video coding standards, such as H.264, have adopted weighted prediction to improve coding efficiency in certain conditions. However, conventional techniques rely on a relatively long window of pictures to observe enough statistics for accurate fade detection. Such methods require the availability of the statistics for the entire fade duration, which introduces long delays that are impractical in a real-time encoding system. Also, conventional parameter estimation methods are only empirical, not mathematically correct.